In many industrial processes, undesirable excess heat is removed by the use of heat exchangers in which water is used as the heat exchange medium. Copper and copper-bearing alloys are often used in the fabrication of such heat exchangers, as well as in other parts in contact with the cooling water, such as pump impellers, stators and valve parts.
The cooling water systems most often used are of the recirculating type where the water is used repetitively and, as a result, remains in extended contact with the metals of the cooling water system. The cooling water is often corrosive towards these metals given the ions present and the intentional introduction of oxidizing substances for biological growth control. In refinery operations, these cooling waters are often contaminated by "sour" leaks which result in hydrocarbons, sulfides, polysulfides, and hydrogen sulfide being present in the cooling water.
These contaminants can become problematic if they are left untreated and can quickly overwhelm any standard operating treatment. The hydrocarbons can coat the metal surfaces of the cooling system and prevent corrosion inhibitors from working correctly. Sulfide ions can cause severe corrosion of metals and are particularly corrosive of copper and its alloys, such as brass and admiralty metal.
Hydrogen sulfide will penetrate copper metallurgy and will form cupric sulfide. The consequences of such corrosion are the loss of metal from the equipment, leading to failure or requiring expensive maintenance, creation of insoluble corrosion product films on the heat exchange surfaces leading to decreased heat transfer and subsequent loss of productivity. Discharge of copper ions can result in them "plating out" on less noble metal surfaces, such as iron, and cause severe galvanic corrosion. Copper discharge is also a health and environmental concern due to its toxicity.
Steel corrosion is a degradative electrochemical reaction of the metal with its environment. Simply stated, it is the reversion of refined metals to their natural state. For instance, iron ore is iron oxide which is refined into steel. Corrosion of the steel results in the formation of iron oxide which, if left unattended, may result in failure or even destruction of the metal.